1. Field of the invention
The present invention relates to a syringe which permits a fluid to be injected into the body while causing no pain following the piercing of its needle by utilizing the anesthetic effect obtained with the use of a cooling gas.
2. Description of the Prior Art
An attempt has hitherto been made to perform a medical injection while applying in advance a surface anesthetic medicine for example, onto a part of the body from which a syringe needle is to be pierced, so as to mitigate the pain involved as much as possible.
Further, when performing a minor operation for example, sometimes, a cooling gas is applied locally onto the affected or diseased part for purpose of local anesthesia, to thereby anesthetize the same by the cooling action occurring at the time of evaporation.
However, when, as mentioned above, a surface anesthetic is applied to the diseased part to give an injection, the part is not anesthetized to a sufficient extent when it is located at a hard portion such as gums. This requires the injection of an anesthetic medicine by means of a syringe. However, the piercing per se of a syringe needle is followed by a pain, which is counted among the problems occurring with the use of the prior technique.